Saliva output is age-stable in healthy persons, yet many older adults complain of a dry mouth. Dehydration is a common disorder in the elderly, and has been hypothesized to cause salivary hypofunction. The purpose of this study was to objectively measure salivary function during a period of dehydration in young and old people, and determine if dehydration, rehydration, age, and gender significantly influence salivary gland flow rates.